Parallaxes of five L Dwarfs with a Robotic Telescope

We report the parallax and proper motion of five L dwarfs obtained with observations from the robotic Liverpool Telescope. Our derived proper motions are consistent with published values and have considerably smaller errors. Based on our spectral type versus absolute magnitude diagram, we do not find any evidence for binaries among our sample, or, at least no comparable mass binaries. Their space velocities locate them within the thin disk and based on the model comparisons they have solar-like abundances. For all five objects, we derived effective temperature, luminosity, radius, gravity and mass from a evolutionary model(CBA00) and our measured parallax; for three of the objects, we derived their effective temperature by integrating observed optical and near-infrared spectra and model spectra(BSH06 or BT-Dusty respectively) at longer wavelengths to obtain bolometric flux and then using the classical Stefan-Boltzmann law: generally the three temperatures for one object derived using two different methods with three models are consistent, while at lower temperature(e.g. for L3) the differences among the three temperatures are slightly larger than that at higher temperature(e.g. for L1). Subject headings: stars: brown dwarfs, parallax, proper motion — Data Analysis and Techniques